Yes, you can cast Flame Blade while holding a shield. In general, you need one free hand to cast a spell. Any material and somatic components required can be performed jointly with that one hand. There's nothing in the description of flame blade that requires a second free hand, so this rule is not superseded. Thus, you can hold a shield in your left hand, cast flame blade with your right hand, receive the blade in your right hand, and happily immolate your foes as you please.

As for concentration, unless something specifically says otherwise, it is only broken by the caster's conscious decision, by taking damage, or by casting another concentration spell.

My understanding of control flame is that you can have up to 3 of its effects as stated in the spell description. To my knowledge and as stated on P205 of the PHB same spell effects do not stack.

The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect-such as the highest bonus-from those castings applies while their durations overlap.

For example, if two clerics cast bless on the same target, that character gains the spell's benefit only once; he or she doesn't get to roll two bonus dice.

So in answer to your question, no you cannot make a torch shed light for 160ft of light. You could however for example expand the flame, double the brightness and manipulate it all in the castings.